1. Field of the Invention
This invention relates generally to an industrial robot and more particularly to a simplified industrial robot having a light weight rectangular main extend shaft that is mounted for longitudinal movement on a plurality of simple adjustable cam followers.
2. Description of the Prior Art
Industrial robot is a generic name for a mechanized apparatus that has the ability to pick up a work piece, perform a work function on the work piece and place the work piece down in a different position. An industrial robot is generally considered to be a more complex structure than a conventional material transfer device which merely picks up an object such as a can or the like by means of a suction cup or other such device and moves it from one location to another location, with the starting and ending locations usually being the same distance from a central pivot axis. Typically, an industrial robot, in addition to having the ability to pick up an object and move the object to a different position with respect to a vertical axis, also has the ability to move the object to a different radius with respect to the vertical axis by means of a horizontal extend cylinder pivoted about the vertical axis. Also, some industrial robots have the ability to tilt or raise and lower the main extend cylinder so as to raise and lower the work piece handling device at the end of the main extend cylinder.
Heretofore, industrial robots have been extremely complex and expensive pieces of machinery and have accordingly been too expensive to employ in many tedious or hazardous industrial operations where profit margins are not sufficient to sustain the overhead involved in the purchase of such a machine.
One of the principal expenses involved in prior industrial robots is the extendable shaft and bearing assembly for moving a work piece to different radial distances from the vertical axis of rotation of the industrial robot. Heretofore, the main extend shafts have been expensive, machined rods, and the bearing assemblies have been elaborate and complex bearing mechanisms specifically designed and fabricated for that use. Such extend shafts and bearing assemblies have been expensive and difficult to align and have provided little or no adjustment for wear or misalignment of the extend shaft.
Another problem with main extend shafts previously employed is that typically such shafts have been cylindrical in shape, with a circular cross-section. Although closer tolerences are sometimes possible with a shaft having a circular cross-section (this seems to be the reason for employing cylindrical shafts), an important drawback with such a shaft is that a cylindrical shaft by itself possesses no resistance to torsional stresses placed on the bar. To provide adequate torsional rigidity in an industrial robot employing a cylindrical extend shaft it has been necessary in previous apparatus to either employ a pair of parallel main extend shafts spaced apart on the apparatus or to fasten an outrigger or a flat strip or key along the outside surface of the shaft and constrain rotation of the shaft by cam followers bearing on the strip. These devices naturally increase the cost and alignment and adjustment problems of the apparatus.
A further problem with prior industrial robots is that most of these robots have employed unduly expensive and inaccurate drive and control mechanisms. In hydraulic control mechanisms heretofore used, most applications have employed electronic servo valve controls in order to provide continuous variation of the rotational and extension positions of the tooling assemblies of the industrial robots. These servo valve mechanisms require complex feedback controls in order to obtain accurate positioning, and even then the systems possess inaccuracies that are impossible to overcome entirely. This is particularly true when the system is bearing a heavy load and the moving members have developed considerable kinetic energy. In such a case, it is difficult to stop and accurately position the extendable arm of an industrial robot.
In systems that employ electric drive motors for rotating and extending the tooling assemblies of an industrial robot, the same type of feedback controls are necessary in order to achieve accurate positioning, and another drawback with this type of system is that considerably less power is available with a conventional electric motor than with hydraulic controls. In order to handle the heavy tooling assembly or heavy work piece, it would be necessary to employ an extremely large and cumbersome electric motor, whereas a simple 1 1/2 inch hydraulic cylinder will deliver the same power under the same situation. Accordingly, an electrically driven apparatus is inadequate for an industrial robot designed for heavy jobs.
With new federal safety standards being enacted every day, there is a need in the industrial trade for a simple and inexpensive industrial robot that can be used in hazardous material handling operations, where the use of manual labor might be unduly dangerous. Further, there is a general need for an industrial robot that can handle heavy loads and can position the loads accurately.
The present invention obviates the foregoing deficiencies of the prior art and provides a simple, inexpensive, heavy duty industrial robot that is capable of a wide variety of material handling needs.